Data compression is often used by storage systems to reduce storage space usage and storage cost.
Compression can be applied to selected storage entities (storage devices, logical volumes or file systems). Data stored in a storage system can be written by different sources/applications and may have various data characteristics with different compressibility. Thus, different storage entities, once compressed, may achieve different compression ratio. Some storage entities may achieve poor compression ratio, either because the original data is already compressed (e.g., compressed video) or because of other characteristics of the data.
Compressing a storage entity is an intensive process that consumes vast computing resources. Compressing data as part of the storing process is also resource consuming that affects the performance of the storage system.
Therefore, selecting storage entities for compression should be done with caution.